Spell crystals are the physical manifestation of summoning and divination spells on the Outer Planes. They move through the planes, seeking the destinations their casters intended for them, but sometimes they get intercepted or eaten by demaraxes or nets+of+crystal+capturing.
If someone other than the intended recipient touches a crystal, they are summoned or interrogated in the intended recipient's place. Demaraxes are immune - to them, it's just a tasty snack.
Sources:
Planescape Campaign Setting
Planescape Monstrous Compendium Appendix II
- 392 reads